1. Technical Field
The present invention relates to a foam duct including foam resin.
2. Related Art
As the duct for vehicles such as cars, a foam duct including foam resin is employed. The foam duct is less heavy than a duct including non-foam resin and is hence suitable for vehicles the weight of which is desired to be reduced from a viewpoint of fuel efficiency and the like.
The foam duct of this kind is ordinarily produced in the following molding method. First, a foam resin prepared by melting and kneading various materials is extruded from an annular die of an extruding machine to form a cylindrical foam parison. The foam parison is clamped by a metallic mold and then air is blown into the foam parison in the metallic mold to push the foam parison against a cavity of the metallic mold to thereby shape the foam parison. The foam parison is then extended to be molded in a contour of the cavity. Thereafter, the molded item having the cavity contour is cooled. The mold is then opened. The molded item is removed and undesired portions thereof are removed, to thereby obtain a desired foam duct.
Document for the foam duct includes, for example, Patent Document 1 (Japanese Patent Laid-Open Ser. No. 2011-194700) and Patent Document 2 (Japanese Patent Laid-Open Ser. No. 2011-116120).
According to Patent Document 1, it is possible, by defining each material of the foam resin, to mold a lightweight foam duct having a sufficient property against low-temperature shock by using less expensive material composition and by decreasing the kinds of mixing materials.
According to Patent Document 2, it is possible, by defining polypropylene-based resins constituting the foam resin, to mold a foam duct with a high expansion ratio in which pinholes are not easily formed even with a high blow ratio.